Research will be continued on the structure and mechanism of action of 2-keto-4-hydroxyglutarate aldolase, a key enzyme involved in the metabolism of L-hydroxyproline by mammals. Our efforts include an exploration of the functional aminoacyl groups that participate in the catalytic process, isolation of active-site peptides, and general establishment of structure-function relationships. Since we have the enzyme in pure form from extracts of bovine liver, bovine kidney, and E. coli, comparative enzymology is done. Studies will be initiated, in vivo and in vitro, on the metabolism and enzymology of gamma-methyleneglutamic acid. Further efforts will be made to purify and characterize D-1-amino-2-propanol:NADO oxidoreductase; the mechanism of action of L-threonine dehydrogenase will be examined. Both of these enzymes are found in animals and bacteria and are involved in the catabolism of L-threonine.